This invention relates to systems for quantizing PCM coded picture elements (pels) of grey level and color images.
To digitally store or transmit grey level pictorial information over digital facilities, the image is subdivided into small picture elements (pels) and the grey level of each pel is encoded. Color images are similarly subdivided and the red (R), green (G) and blue (B) component levels of each pel are individually encoded. Since each image will generally contain a large number of pels and since each pel will generally be encoded into several bits, a substantial amount of storage is required for each image or a substantial amount of transmission time is required. It is therefore desirable to reduce the number of bits into which each pel is encoded. Prior art quantization schemes that quantize the grey level or color components of each pel into a fewer number of levels generally suffer noticeable degradation in the quality of the stored or received image.